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Jca50H / 100h/ 22h mod thread and owners club

01-09-2012, 06:31 AM

I say the main difference is a the pots are 1m instead of 500k making the jca sounding a bit darker and a 100k plate resistor for one of the loops stages. I'm going to work on the warren haynes mod, the depth mod, the scoop mod and the clean/ crunch mod an a couple of others. I'm also going to fix the layout of the thread soon. and some cosmetic mods too, I want to retolex in white snakeskin and I want to do a metal grill.

The thread is a work in progress so check back often and don't be afraid to discuss and join in! What mods do you want to see?

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Jca 50h/ 100h/ 22h Mod thread and Owners Club
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I'll add the crunch/clean switch, the bright switches and the scoop mod individually that way it doesn't overwhelm some one who just wants the basic aggressive stock s.l.o sound.

Numbering is for the 50H

The Predator mod

A high gain metal mod for both channels. changes up the lead channel a bit and adds the sucker punch to the crunch channel. The change in r36 is optional.

Numbering is for the 50h

The sucker punch mod:

r34= 680k

c23=250pf

This mod only affects the "crunch channel" not the lead channel

The resistor numbers for this are for the 50h

Simple clean channel:

This is the less involved simple way to do it, for the beginner. You can make it switchable. basically you add a 39k resistor to ground after r42 an before the gain pot. I think dues has 68k in his and say it sounds "punchier".

The resistor numbering is for the 50h

Simple crunch channel:

So you want more gain huh? replace r42 with a 470k resistor (Or solder another 1m resistor in parallel with the stock r42) and replace c28 with a 470pf cap ( i recommend a silver mica cap). There you go gainiac.

The resistor numbering is for the 50H

S.l.o. clean/crunch switch:

Use a dpdt switch to put 470k resistor in series with another one making the total resistance close to 1m (aka the stock value) and adding a 39k resistor to ground. When the switch is activated the first 470k resistor is out of the circuit along with the 39k resistor to ground and you have a resistance of 470k aka the crunch mode. Same concept as the "simple" versions of this.

The resistor numbering is for the 50h

Decadence Mod

Similar to the clean/crunch mod except this gives you a crunch AND a better clean channel.

The resistor numbering is for the 50H

Simple scoop mod

The simple scoop mod is a basically a t-filter. You replace r34 with 2 1m resistors in series with a .001uf cap soldered from the middle of the resistors to ground.My version has a standard 22uf fenderish cathode bypass cap on r 45 and is switchable.

Depth

So basically Your looking at the pot exactly like this. the above just illustrates the resistor number for the nfb resistor and to what output jack you connect it to.

also in case you have a 20h and want to join the fun here's the 20h mod thread.

Comment

Haven't used my JCA in a band situation in a few months - took it to a jam session this weekend and killed it. Got some really killer tones and more gain than I could want for the radio rock songs we played.

I am debating picking up one of the Peavey Vypyr 30 heads and a Sanpera for ease of use though - built in FX + modeling to use at home/leave at the practice space while the JCA I can save for when I need solid tone.

Comment

I hadn't played my JCA50H in about a week, but when I went to the basement (My guitar room) I noticed that I had left my amp on

Everything seems fine, but was wondering if it had any effect on my tubes since they had been on for a week straight. I also want to soon replace all of the tubes to warm the tone up a bit, what are the best tubes (that you guys have found) to warm this head up?

Comment

interesting...what exactly does this sucker punch mod do to the sound?

More gain on the crunch channel and it break up quicker.

Originally Posted by cscbo1

I hadn't played my JCA50H in about a week, but when I went to the basement (My guitar room) I noticed that I had left my amp on

Everything seems fine, but was wondering if it had any effect on my tubes since they had been on for a week straight. I also want to soon replace all of the tubes to warm the tone up a bit, what are the best tubes (that you guys have found) to warm this head up?

I haven't had a chance to play around with tubes too much, just the stock chinese. I hear that a 12au7 in v1 make it sounds marshallish on the lead and super clean on the crunch channel.

Originally Posted by FastRedPonyCar

SLO preamp circuit mod and KT66's were the best decision for my 100H. Really helped the lead channel a lot.

clean channel right out of the box is really nice though.

How are the kt66s compared to 6l6s btw? Thats another change I'm interested in. Btw did zach change your pot values (for the gain controls) or did he keep them at 1m?

Jca 50h/ 100h/ 22h Mod thread and Owners Club
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Comment

Been reading about your mods for the JCA50 and want to have a go at your SLO mod. Never done this before although I have done repairs on my amps like fixing dry joints, re biasing and retubing - pretty basic stuff really. Anyway wonder if you could answer a couple of quick questions.

In your schematic c21 is a 470pF cap. Can't make out the replacement too well on my screen but think you say to replace it with 1nF cap (1 nano Farad I think). Is that right?

Also what caps will work best, silver mica perhaps? Any particular type of resistor best to use?

Comment

Haven't used my JCA in a band situation in a few months - took it to a jam session this weekend and killed it. Got some really killer tones and more gain than I could want for the radio rock songs we played.

I am debating picking up one of the Peavey Vypyr 30 heads and a Sanpera for ease of use though - built in FX + modeling to use at home/leave at the practice space while the JCA I can save for when I need solid tone.

I have both the JCA100H and Vypyr 30 head. I think you'll be surprised at how loud the Vypyr 30 can get, yet still sound as good as it does at lower volumes.

The only one I can confirm is the JCA22H. I'm not sure if the 100H/100HDM/50H does or not. Seems there's a thread around here where someone from Jet City says the loop was done differently for the 22H due to complaints...which I don't know if that includes all previous models or not. Seems most Soldano and Soldano-designed amps have the same issue with loops that don't work quite right with pedals.